Materials Science Forum Vol. 969

Abstract: Present study is planned to analyze the effects of welding process parameters on quality characteristics of TIG welded 316L austenitic stainless steels (ASS). The input parameters considered in the study are: welding current, speed and gas flow rate. Butt-joints of ASS sheets have been made as per Box-Behnken design of response surface methodology (RSM). After welding operation, tensile tests have been conducted on welded samples and observations of ultimate tensile strength (UTS) has been noted. Mathematical modeling has been made to relate the input parameters and output response by RSM. Teaching leaning-based optimization (TLBO) approach has been used to optimize the UTS. The influences of input welding parameters on UTS has been studied and analyzed through contour plots. Confirmatory tests have been conducted to validate the predicted parametric condition obtained by integrated RSM and TLBO. From the study, it is found that RSM and TLBO is efficient to maximize UTS in TIG welding operation.

Abstract: In this study, an attempt has been made to develop a predictive model for tool nose wear. A well planned experimental design was utilized for this purpose using the design of experiment approach. From this research work, it was found that cutting speed (s), feed (f) and their interaction having the main effect on cutting tool performance. Using ANOVA analysis significance and contribution of each machining parameter and their interaction is also analyzed. Hence, a predictive model was developed to predict tool nose wear by using the various machining parameters and its adequacy was also checked for the prediction purpose.

Abstract: Many difficult to machine materials, such as Inconel 625Ni-based super alloy, are uncommon class of metallic materials with exceptional combination of greater thermal strength, toughness and resistance to deterioration. They have extensive applications in the manufacturing of new aero-engines, besides its enormous uses in marine, chemical and oil & petrochemical industries. In the context of its wide range of applications, there is a need for efficiently processing better methods in the manufacturing of such difficult to machine materials. This study consists of the turning operation of Ni-based super alloy Inconel 625 without coolant, carried out by physical vapour deposition (PVD) coated carbide inserts. The response parameters, such as surface roughness and material removal rate were evaluated in terms of cutting speed, feed rate and depth of cut. Sixteen experiments were carried out, based on Taguchi's Design of Experiments using orthogonal array. The resulting analysis was done based on response graph. The experimental results revealed that the feed rate was the most influential factor, followed by the depth of cut and cutting speed. The optimal parameters achieved were cutting speed of 90 m/min, the feed rate of 0.35 mm/rev and the depth of cut 0.2 mm.

Abstract: Nickel based super alloys, such as Inconel 625 is amongst the most difficult to machine, due to its low thermal conductivity and high strength at higher temperature. Although, they are used in aerospace exhaust systems and other applications, the strain hardening that results during the machining operation, which adversely affects surface integrity of machined surface of such materials especially in extensive applications, is a cause for concern. In this context, this study was carried out, involving the milling operation, using solid carbide tools coated with TiAlSiN, under specifically developed conditions for dry machining of the difficult to cut materials. The cutting parameters were 4 in number, namely radial rake angle, feed per tooth, cutting speed and radial depth of cut and the response parameters included surface integrity characteristics, such as residual stresses, surface roughness and micro-hardness. Based on the experimental analyses, it was found that the micro-hardness of machined surface was higher. Micro hardness of sub surface decreases with the depth (50,100,150,250μm) due to a reduction in the work hardening of the Inconel 625, underneath the surface layer. The residual stresses were analyzed using main effect plot, and it was seen that the residual stresses were significantly influenced by the radial rake angle, followed by feed per tooth.

Abstract: Tungsten inert gas (TIG) arc welding–brazing has been recently developed and is being increasingly implemented in various industrial applications. Nowadays, this process gains much attention in joining of dissimilar metal combinations. This review paper explains the principles underlying TIG arc welding – brazing of dissimilar metal combinations and highlights the above benefits in a number of practical applications. The process mechanism of TIG brazing is different from the conventional welding processes and it will bridge the gap between the two substrates by the addition of fillers under the concentrated heat source of TIG electrode. TIG brazing technique is one of the best alternative process among the other joining process for effective joining of dissimilar metals, which have various melting temperatures and physical properties. It is very important to understand the process mechanism and its compatibility with the various dissimilar materials joining. The present study focuses on the addressing of progress of TIG brazing process in modern days and its applications in the various industries, and to bring the awareness to the manufacturers about the importance of this process from this review report. Keywords: Tungsten inert gas (TIG) arc welding–brazing, Dissimilar metals, Microstructures, Mechanical properties.

Abstract: In this Paper, the application of Taguchi Method (TM) on the process parameters of Injection Moulding of Polybutylene Terephthalate (PBT) is presented. The influence of process parameters, such as Injection Pressure, Suckback Pressure, Injection Time, Cooling Time, Zone 1 Temperature & Zone 2 Temperature (Barrel Temperatures) on Dark Spots and Short Shots (defects) were investigated using the Orthogonal Array L₁₆ of Taguchi Method for 6 factors at 2 levels each with the response being percent defectives. It was found that Injection Pressure, Injection Time & Zone 1 Temperature had a major effect on the response. After the application of Taguchi Method, the rejection rate dropped down to 5.84% from 11.33%, which is a 48.45% reduction.

Abstract: Difficult-to-cut materials, generally high hardness, strength and toughness, are generally difficult to machine in conventional machining. Also tool wear is high in conventional machining processes. Wire Cut Electric Discharge (WEDM) machining is particularly used for machining complex profiles, demanding very high accuracy. The current work focuses on the optimization of roughness of a surface that is machined using WEDM; the process parameters considered for optimization are pulse-on-time (P_on), pulse-off time (P_off), wire feedrate (WFR) and spark gap voltage (SGV). One of the surface integrity aspect is considered as surface roughness (SR) and other related to machining output considered as material removal rate (MRR) for the output responses. The paper presents, a multi-criteria decision making technique, with Grey Relational Analysis (GRA) integrated with Particle Swarm Optimization (PSO) for optimizing the process parameters. Further, confirmation tests that were conducted also validated the improvement in SR and MRR.

Abstract: The aim of this research article is to study the static mechanical properties and abrasive wear behavior of epoxy biocomposites reinforced with different weight percentage of waste silk fibers. The effect of parameters such as velocity (A), load (B), fiber loading (C) and abrading distance (D) on abrasive wear has been considered using Taguchi's L₂₅ orthogonal array. The objective is to examine parameters which significantly affect the abrasive wear of biocomposites. The addition of silk fiber has resulted in improved flexural properties of the epoxy matrix. The results of ANOVA indicated that the parameter which played a significant role was abrading distance followed by fiber loading, load and sliding velocity.

Abstract: Grain refinement is one of the most important and popular melt treatment process for Al-Si alloy casting. Microstructure and mechanical properties of commercially available Aluminium Silicon alloy LM6 can be improved with the addition of grain refiners and modifiers as these provide technical and economic advantages. This paper is an effort to study the effects of addition of grain refiners and modifiers to the eutectic Al – Si alloy LM6. Commercially available Al - Si alloy LM6 (eutectic = 12% Si) is grain refined with Al-5Ti-1B and Al-3B; and modified with Al-10Sr master alloys. These were added individually and then tested for its unique mechanical properties such as ultimate tensile strength, hardness and wear; which are co-related with the machining tests such as turning, surface roughness and drilling. The test results are compared with microstructure of the samples observed through SEM.The mechanical properties of this alloy can be altered after addition of master alloys, which in turn alter the grain size. Thus the results conclude that the mechanical properties of Al-Si alloys in general are controlled by a number of principal microstructural features. A fine grain size is desirable, leading to improvement of mechanical properties.

Abstract: Wire Cut Electrical Discharge Machining (WEDM) is a non-conventional thermal machining process which is capable of accurately machine alloys having high hardness or part having complex shapes that are very difficult to be machined by the conventional machining processes. The WEDM finds applications in automobiles, aero–space, medical instruments, tool and die industries, etc. The input parameters considered for WEDM are pulse on time, pulse off time, flushing pressure, servo voltage, wire feed rate and wire tension. Performance of WEDM is mainly assessed by output variables such as, material removal rate (MRR), kerf width (Kw) and surface roughness (Ra) of the work piece being machined. Looking at the need of a suitable optimization model, the present work explores the feasibility of machine learning concepts to predict optimum surface roughness and kerf width simultaneously by making use of experimental data available in the literature for machining of Hastelloy C– 276 using WEDM. In most of the literatures, single objective optimization has been carried out for predicting optimum cutting parameters for WEDM. Hence, the present work presents a methodology that makes use of a machine learning algorithm namely, gradient descent method as an optimization technique to optimize both surface roughness and kerf width simultaneously (multi objective optimization) and compare the results with the existing literatures. It was observed that the input parameters such as pulse on time, pulse off time, and peak current have significant effect on both surface roughness and kerf width. The gradient descent method was successfully used for predicting the optimum values of response variables.